Laser systems typically use a cylindrically shaped gain medium (laser rod) to generate a laser output. The gain medium is pumped by a light input from an optical pump source to excite the gain medium. A laser resonator is formed whereby a pulsed or continuous wave intracavity laser beam is generated and amplified by the excited gain medium as it travels through the gain medium. A portion of the intracavity laser beam is coupled out of the laser resonator to form the laser output.
Heat is generated during excitation of the gain medium. A cooling system is used to maintain the gain medium within a desired operating temperature range. Such cooling systems typically include a cooling jacket that surrounds the gain medium. Cooling liquid is circulated through the cooling jacket to extract heat from the gain medium.
In high power laser systems (e.g., more than 100 watts), power cycling of the optical pump source causes the gain medium to undergo significant temperature changes. Such temperature changes result in the thermal expansion and contraction of the gain medium, which can cause failure of the laser system as a result of movement of the gain medium within the cooling system.